Instruments for determining the wave impedance of a material have been developed using many different sensing technologies that comprise separate components operating with different electromagnetic modalities. Related developments, including antennas and RFID tags, have been developed.
A planar loop antenna with a balun has been developed within a communication transceiver in U.S. Pat. No. 6,593,886. A communication link is disclosed as attenuated by a material.
An annular ring induction-type antenna is disclosed in U.S. Pat. No. 6,992,630, comprised of a plurality of circular rings operational within a communications system. The antenna is driven through an inner magnetically-coupled feed ring acting as a non-resonant coupler.
A prior art example of an antenna coupled into an adjacent medium is disclosed in U.S. Pat. No. 9,916,528. This wireless sensor determines a signal strength of radio-frequency energy emitted by an RFID tag wherein a signal strength is affected by the frozen or thawed state of a material disposed proximally with the tag. The sensing structure is an RFID tag.
In other prior art related to measurement of wave impedance of a material, a semi-passive transponder is disclosed in U.S. Patent Application 2017/0237466. This transponder is powered by RF energy harvesting. Energy harvesting is implemented via a resonant voltage multiplication circuit. A voltage multiplication circuit permits harvesting charge in nano- and micro-Joule increments to provide a transponder voltage higher than would otherwise be possible without the multiplier. RF energy is converted to a DC-level and stored over time to provide accumulated energy adequate to power full operation of the transponder.
There is a need for an impedance spectrometer sensing wave impedance of a material providing features of increased miniaturization, increased sensitivity and accuracy, increased tolerance to RF blocking environments, extended range and sensing for an increased number of material types.